1. Field of the Invention
The present invention relates to a novel recording liquid improved in indoor color change resistance and pitch-blackness, and an ink-jet recording process using the recording liquid.
2. Related Background Art
Water-based inks comprising a water-soluble dye dissolved in a water-based medium have been hitherto used as inks for fountain pens and felt pens and as inks used for ink-jet recording. In these water-based inks, water-soluble organic solvents are commonly added so that pen points or ink ejection nozzles can be prevented from being clogged with ink.
It is required for these conventional inks to give an image with a sufficient density, not to cause any clogging at pen points or nozzles, to have good drying properties on recording mediums, to suffer less feathering, to have excellent shelf stability, and, particularly in ink-jet recording systems utilizing heat energy, to have excellent thermal resistance. It is also required for the image formed to have a sufficient light-resistance and water resistance.
Inks with various hues are also prepared from dyes with various hues. Of these, black inks, which are used in both monocolor and full-color images, are most important inks. As dyes for these black inks, C.I. Food Black 2 has been mainly used taking account of various performances (see Japanese Patent Application Laid-Open Nos. 59-93766 and 59-93768).
Incidentally, among the above various required performances, what has been particularly a serious question in recent years is the weathering resistance of images.
In regard to the weathering resistance of images, what hitherto has been a mainly serious question is the problem of color fading due to direct sunlight or any kind of illumination (so-called light-resistance). Such a problem of color fading has been attempted to be resolved by the selection of dyes having superior light-resistance.
Recently, however, the problem of color changes of images has become important, in addition to the above discussed problem of color fading. Namely, images formed by conventional inks have not only the problem of color fading but also the problem of color changes. The color changes refer to changes in hues while there are less changes in density. In black inks particularly used in the largest amount, there is a problem of the browning that black turns brown. In particular, in the instance of full-color images, this browning results in a rapid lowering of image quality.
This problem of browning occurs even in a room without exposure to direct sunlight. The browning is also accelerated depending on the types of recording mediums on which images are formed, and this problem of browning has been unavoidable with respect and the C.I. Food black 2 that has been hitherto widely used.
In particular, in the instance of so-called coated papers comprising a substrate such as paper and an ink-receiving layer which contains a pigment and a binder and which is formed on the substrate, the browning may seriously occur even with use of inks that may cause less problem of color change in the instance of plain papers. This problem has been unresolved by the mere selection of dyes having superior light-resistance.